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1、* Revision submitted by ICAC on August 18, 2004ICAC Proposed Conditional Test Method (CTM-042)*Use of Flame Ionization Detector-Methane Cutter Analysis Systems for VOC Compliance Testing of Bakeries1.0BackgroundPerformance testing of volatile organic compounds (VOC) destruction devices such as therm
2、al oxidizers and catalytic oxidizers require simultaneous measurements of non- methane hydrocarbons (NMHC) in the gas streams entering and exiting the destruction device. In the past, continuous total hydrocarbon measurements employing testing protocol in accordance with U.S. EPA Test Method 25A (Ga
3、seous Organic Concentration - Flame Ionization) has been combined with laboratory analysis of grab samples taken hourly. This approach has been demonstrated to be labor intensive, costly and does not provide real-time measurements necessary to evaluate the performance of the thermal or catalytic oxi
4、dizer.2.0PurposeUse of this method is limited to measuring VOC emissions from bakeries. The purpose of this Conditional Test Method (CTM) is to provide an alternate method for making real- time non-methane hydrocarbon measurements for providing immediate information regarding performance of the VOC
5、destruction device. This method describes the use of a hot flame ionization detector (FID) based instrument equipped with a catalytic methane cutter in conjunction with U.S. EPA Test Method 25A to provide real-time differential measurement of total hydrocarbons, methane and by difference non-methane
6、 hydrocarbons.This CTM is directly applicable to large commercial bakeries. The measurement of VOCs in bakeries is required to verify air pollution control equipment destruction efficiency as required by various state regulations. The large majority of these state regulations are State Implementatio
7、n Plan (SIP) driven. A minority of states have “State Only” legislation requiring oxidizes, and testing of them, on bakeries.Extensive commercial data has been gathered from large commercial bakeries, where exhaust gases from ovens baking bread, crackers and other yeast products are tested. These ex
8、haust streams typically contain ethanol in concentrations of 1,000 to 5,000 ppm, methane in concentrations of 50 to 1000 ppm and moisture at 2 to 15%. A catalytic oxidizer on this application will destroy 95-99% of the non-methane hydrocarbons, reducing the ethanol to concentrations of 10 ppm to 250
9、 ppm in the oxidizer exhaust. The other compounds will virtually maintain their concentrations. Due to the large amounts of moisture and the water solubility of the non-methane hydrocarbon, condensation must be avoided. The relatively large amount of methane to non-methane hydrocarbon, especially in
10、 the oxidizer exhaust, makes it more important to make this measurement by one technique. * Revision submitted by ICAC on August 18, 20043.0Technical ApproachA heated flame ionization analyzer (HFIA) when equipped with a catalytic methane cutter upstream of the detector accepts a continuous flow of
11、sample delivered by a heat traced sample line maintained above 375F. A catalytic methane cutter is a catalytic device consisting of catalyst in a reactor designed by type of catalyst and operating temperature to combust all non-methane hydrocarbons and leave only methane. Instrument suppliers provid
12、e different approaches to this technology. There are “single detector/single amplifier” instruments and “dual detector/dual amplifier” instruments. Both types of instruments give measurements of total hydrocarbons and measurements of methane in the stream and by difference they measure non-methane h
13、ydrocarbons.With “single detector/single amplifier instruments, the sample stream is alternately either passed through or around a selective catalytic combustion reactor (methane cutter) before entering the detector, which alternately measures either methane or total hydrocarbons. Instrument softwar
14、e controls the switching times (usually 1-minute cycles) and continuously displays the THC, CH4 and non-methane results.With “dual detector/dual amplifier” instruments, the sample stream is continuously split. Part of the sample goes to a direct measuring detector measuring total hydrocarbons. The o
15、ther part of the sample goes to a selective catalytic combustion reactor (methane cutter) followed by a detector, which continuously measures methane. From either of these instruments, the measurements of total hydrocarbons and measurements of methane are subtracted to give the non-methane hydrocarb
16、on result.FID Theory of OperationThe technique of flame ionization detection (FID) relies on the ionization of molecules during high temperature combustion in the reaction zone of the FID-flame to determine the total hydrocarbon concentration within a gaseous sample. The analyzer has an adjustable heated oven (60 to 200C) which contains a heated sample pump and burner in which a small flame is elevated and sustained by regulated flows of a
